The present invention relates to a procedure for reproduction of a photography in an article of glass. More precisely, the invention concerns a procedure for reproducing coloured pictures, particularly photographies, in an article of glass.
It is already known how to provide a glass-surface with different types of decorations or pictures, e.g. by printing or painting pictures directly on the glas in a manually or mechanized manner. Such methods of applying the pictures however, have the drawback that those have a low durability. Further, such simple applying procedures offer only restricted possibilities of expression, and a lasting high class appearance cannot be attained.
U.S. Pat. No. 5,269,826 describes a process for manufacture of decorated glass-ceramic wares. This process seems in the first instance to be aimed at ceramic hobs, where the wearing out is obvious. Thus, it is desirable to apply a relatively thick layer of paint on the glass surface. This state of the art process comprises a preliminary course of proceeding, which involve a heat treatment of the surface of the glass ware with a Broensted acid at a temperature between 50 and 800° C. Subsequently, the glass is decorated with a ceramic paint, e.g. a commercially available suspension of powder composed of oxides, and with lead borate as a binding agent. Since the pattern has been applied to the article, this will be burned in a kiln. Accordning to the patent, the treatment with Broensted acid results in that the ceramic paint sinks into the glass during the subsequent firing and will cristalize slowly, whereupon the glass surface, despite a thick paint layer, seems relatively even after the firing. This is doubtful seen to the insignificant difference in density between the glass and the ceramic paint, and in respect to the high viscosity of the glass at the firing temperature.
EP-A1 778 154 describes a procedure for multicolour printing on glass and other transparent materials, where the printed picture shall appear luminously transmitting. The printing takes place using a silk screen method and printing ink out of which four colours are used. The inks are intended to dry by use of different physical reactions, out of which drying with visible light during a time of up to 10 seconds is mentioned. No sealing of the ink occur in the glass surface. One more process of multicolour print on a glass surface is known, where the different inks have essentially similar melting points, which are in a temperature range that is uncritical to the glass. The subsequent firing takes place under such a short time as just 2 to 6 minutes and at at temperature of 660° C. at the most. Thus, just the printed ink melt, while the glass remains practically unaffected. The advantage in this known process is that it is rapid and suits well for industrial production.
One problem related to firing ceramic paints on flat standard glass, a so-called float-glass, is the appearance of turbidity on the glass surface and in that way a less transparent glass than before the firing. This phenomenon is denominated coating. It is owing to that the side of float-glass during manufacture lying on the tin bath will be doped with stannous ions. Such ions have an affinity to siliciferous materials like glass, and form the coating.